So you tried another giffgaff sim in the dongle and all worked ok for data, and the dongle sim works for calls in a phone but not data (could be a data block assuming you have all the correct APN settings)
What package did you have on it , a goodybag, a gigabag or just credit
Depend what dongle you are using but I also found this on t-mobiles site for trouble shooting
The 619 error can usually be resolved by taking the steps below:
- Insert the SIM card into a compatible handset. If the handset picks up a signal reinsert the SIM into your USB modem and try the following
- Change connection from 3G to GPRS and try to connect again.
- Remove and re-add the modem on your computer. Click on Start > Control Panel > Modems and remove any instances of your USB Modem. Then plug the modem back into a different USB port (if possible) on the PC/laptop. Once the modem has been detected open connection manager and try connecting again